What is the standard heat of reaction (Delta H^0) for the decomposition of hydrogen peroxide?
2H2O2 (l) ==> 2H2O (l) + O2(g)
To determine the standard heat of reaction (ΔH°) for the decomposition of hydrogen peroxide, we can use Hess's Law or look up the data in a reference source like a thermochemical table.
1. Using Hess's Law:
Hess's Law states that the overall enthalpy change of a reaction is the sum of the enthalpy changes of its individual steps. In this case, we can break down the reaction into a series of steps using known reactions with known enthalpy changes.
First, we need to find reactions with known ΔH° values that can be combined to obtain the desired reaction:
1. The formation of water from its elements:
H2(g) + 1/2 O2(g) → H2O(l)
ΔH1° = -285.83 kJ/mol
2. The formation of hydrogen peroxide from its elements:
H2(g) + O2(g) → H2O2(l)
ΔH2° = -187.8 kJ/mol
Now, by reversing equation 1 and doubling equation 2, we get the desired reaction:
2H2O2(l) → 2H2O(l) + O2(g)
By combining the enthalpy changes, we obtain the ΔH° for the decomposition of hydrogen peroxide:
ΔH° = 2ΔH1° + (-2ΔH2°)
ΔH° = 2(-285.83 kJ/mol) + (-2(-187.8 kJ/mol))
2. Looking up data in a reference source:
Instead of using Hess's Law to calculate ΔH°, you can look up the standard enthalpy change (ΔH°) for the decomposition of hydrogen peroxide in thermochemical tables or online databases that provide thermochemical data.
The standard heat of reaction for the decomposition of hydrogen peroxide is approximately -196.2 kJ/mol.
Please note that the values provided here are hypothetical examples and may not reflect the actual values. It is essential to consult reliable sources to obtain accurate and current thermodynamic data.